I have a 15+ yr old stereo (integrated AM/FM, phono, Amp - with external speakers) that has a pretty good sound and I use for my workshop.

The sound output is now low and a bit distorted (with a slight hum) and checking inside, the heat sinks for the o/p power transistors (both channels) are running very hot (can't touch) - even with the speaker wires disconnected.

I guess something is shorting... but no visible evidence of any problems - eg. the speaker wires aren't touching etc.

Don't want to spend a lot of money on fixing this unit and I'm quite handy with electronic repairs but I'm wondering where the obvious place is to start troubleshooting?

Many thanks for any ideas...